Its 164-kilometre (102 mi) coastline is indented by Paterson Inlet (east), Port Pegasus (south), and Mason Bay (west).

Margaret Cameron-Ash claims that James Cook established the insularity of Stewart Island during his first Pacific voyage in 1770 but decided to hide his discovery for reasons of military and colonial policy.

[8] However, G. A. Mawer argues that Cook was simply unsure whether it was an island because his focus was on finding the southern extent of New Zealand, and conditions were unfavourable for more closely exploring a possible strait.

[9] The strait was first charted by Owen Folger Smith, a New Yorker who had been in Sydney Harbour with Eber Bunker, from whom he probably learned of the eastern seal hunting.

The river rises close to the northwestern coast and flows southeastwards into the large indentation of Paterson Inlet.

The southern half is more uniformly undulating, rising to a ridge that runs south from the valley of the Rakeahua River, which also flows into Paterson Inlet.

One suggestion is that the bay was formed in the aftershock of a meteorite impact in the Tasman Sea; however, no evidence has been found to support such a claim.

Sea levels began to rise 7,000 years ago, eventually separating Stewart Island from the mainland.

A previous settlement, Port Pegasus, once boasted several stores and a post office, and was located on the southern coast of the island.

Another site of former settlement is at Port William, a four-hour walk around the north coast from Oban, where immigrants from the Shetland Islands settled in the early 1870s.

The northern third (north of the Freshwater Valley Fault) is composed of Anglem Complex diorites, minor gabbro and granite, and many pegmatites.

This designation is given for sites in very remote locations to increase awareness of their dark sky characteristics and promote long-term conservation.

The application for accreditation was made by Venture Southland, an agency responsible for the region's economic and community development initiatives and tourism promotion, with the aim of attracting more visitors, particularly in the winter period.

[27] The park covers close to 1,400 square kilometres (540 sq mi),[28] which is about 85% of the area of Stewart Island / Rakiura.

The area of the park excludes the township around Halfmoon Bay (Oban) and some roads as well as private or Māori-owned land further inland.

Although the clay soil is not very fertile, the high rainfall and warm weather mean that the island is densely forested throughout.

Native plants include the world's southernmost dense forest of podocarps (southern conifers) and hardwoods such as rātā and kāmahi in the lowland areas with mānuka shrubland at higher elevations.

Noeline Baker purchased land near Halfmoon Bay in the early 1930s and with a checklist by botanist Leonard Cockayne populated it with all the local indigenous plants.

She gave the land and her house to the government in 1940, and today Moturau Moana is New Zealand's southernmost public garden.

There are even more species of birds, including huge colonies of sooty shearwater and other seabirds, on The Snares and the other smaller islands offshore.

Stewart Island is the sole remaining breeding place of the critically endangered southern New Zealand dotterel.

[34] As the island has always been sparsely populated and there has never been very much logging, much of the original wildlife is intact, including species that have been devastated on the mainland post-colonisation.

[40] The first scheduled service across Foveaux Strait began in 1877 for weekly mail delivery, but soon also carried passengers and general cargo.

The Awarua arrived in Bluff on 4 January 1885, after a delivery voyage lasting more than 6 months since leaving dock in London.

[41] Many different vessels were used by the Bluff Harbour Board on the Foveaux Strait ferry service in the first half of the 20th century, including the Southland and Theresa Ward, MV.

[55] By 1985, the accumulated losses in operating the Wairua on the Foveaux Strait service over the previous 10 years totalled $6 million.

[64] Real Journeys bought out their partners to take complete control of the Stewart Island ferry service in May 2005.

[65][66] In 2015, responding to proposals for subsidised travel to Stewart Island for senior citizens, the chief executive of Real Journeys stated: "Not only are Stewart Island ferries completely unsubsidised but the Foveaux Strait is an extremely expensive piece of water to operate on commercially".

[73] By 1980, a sealed airstrip had been built at Ryan's Creek above Oban, and services from Invercargill were provided using Nomad and Britten-Norman Islander aircraft.

In 1998 a Southern Air Cessna ditched into Foveaux Strait on a trip from Stewart Island to Invercargill after losing power to both engines, resulting in five deaths.